It is known to preserve and distribute music in various digital audio file formats. Though a retail customer may own a legally purchased physical embodiment of the digital music file, such as an optical CD or other computer storage media that holds a properly downloaded copy of the music, copyright law reserves to the owner of the copyright the right to make and distribute additional copies of the file. The owners of music copyrights have only recently allayed concerns over unauthorized copying and distribution over a network, and have now licensed content providers to copy and distribute digital versions of their copyrighted songs over the internet.
Due to the significantly larger size of digital media files that carry video content as opposed to only audio, the combination of file compression and bandwidth expansion necessary to electronically send video in less time than it takes to run or ‘play’ the video file at normal speed has only recently been achieved. With that technological barrier overcome, some business analysts expect that precedents set by the music industry will eventually be followed by the cinematic industry. For brevity, the above audio and video files are referred to as media files, and includes music, movies, video clips such as movie trailers and similar short advertisements, and the like. A copy of such a media file obtained via download from a network (with no accompanying transfer of storage media) is referred to as a virtual copy of the media file. Though the following discussion relates primarily to music files, the principles apply to any media files.
Virtual music is generally downloaded over the internet onto a personal computer. Retail customers often upload the music files stored on their PC to a portable digital music device, such as an iPod®. Portable digital music devices are relatively new consumer products, and consumers are generally satisfied with the memory volume available (now typically 10-40 gigabytes). As music downloads became more commonplace, many PC users were linked to the internet or local network via a dial-up modem and a standard telephone line. The need soon arose to compress music files so that transfers over a network would not occupy inordinate amounts of bandwidth. This also allowed portable music players to store more music, and greatly contributed to their quick adoption by the marketplace.
Digital music files are encoded and compressed using an algorithm (or lookup table) that is termed a codec (code/decode). Because the commercial transfer of compressed digital music is becoming ubiquitous, the value of the codec used to compress them has risen in value. Several different companies have introduced their own codec to capture some of that value, which can be achieved directly by licensing the codec or indirectly by providing such a critical mass of files requiring that codec as to drive users' choices of hardware. For example, MP3, AAC (Advanced Audio Coding, sometimes termed Mpeg-4 Audio) and AAC+ are each well-known codecs currently in use among the general public. Microsoft® has recently introduced a WMA codec to compete with MP3 by using approximately half the storage capacity for what some users have reported is equal or better sound quality. Where MP3 and AAC are optimized for playback at compression rates above 64 kbps, AAC+ is a codec optimized for playback at compression rates below 64 kbps. As a result, MP3 and AAC yield larger music files, whereas AAC+ yields smaller music files, all other factors being equal. Though AAC+ is optimized for lower compression rates, it is inferior (in playback quality) to codecs that produce larger files.
FIG. 1 is a diagram showing relative audio quality or fidelity (vertical axis) for playback at various compression rates (horizontal axis) for different codecs. The lower portion of the shaded regions representing each codec shows worst-case performance, which for AAC LC and AAC LTP are in the range of the much older MP3 format. The MP3, AAC LC and AAC LTP codecs each provide increased fidelity with increased compression rates, whereas maximum fidelity for an AAC+ file is achieved at about 64 kbps compression.
It has been reported that many portable digital music players have the capability to play files using more than one codec but are precluded from doing so by digital rights management (DRM) software that works to preserve the proprietary nature and value of privately owned codecs noted above. Briefly, a file carrying a .MP3 extension, necessitated by the format in which it was downloaded, will be played by the portable digital music player only using the MP3 codec. While the music player might have the capacity to re-compress or other wise convert between .MP3 and, for example, AAC+, it is not authorized to do so absent some means to circumvent the DRM (which may be prohibited by the Digital Millenium Copyright Act). However, the inventor does not perceive that portable digital music need be limited to a dedicated device, as current DRM restrictions tend to do.
It is known to download from a network certain abbreviated music files, such as digital ringtones, that are intended for a mobile station. It is assumed that certain individuals download these ringtones directly to their mobile station when that mobile station includes a browser that accesses the internet via a mobile telephony air interface. The limited bandwidth of that air interface, combined with the limited storage capacity and power supply of a mobile station, make it impractical to provide downloads of larger music files (e.g., an entire two- or three-minute song) over a mobile telephony air interface using codecs designed for the data rates of cable modems and DSLs. Merely using a codec tailored to the environment of a mobile terminal (less storage, lower data throughput over the air interface) is not anticipated to meet the needs of most consumers for the following reason. It is anticipated that consumers will accept that a song played on a mobile terminal may offer only reduced fidelity as compared to a dedicated portable digital music player (e.g., iPod®), at least until certain technological obstacles are overcome. However, those same consumers are likely unwilling to accept that reduced song fidelity when the same song is played in devices that currently offer higher fidelity such as portable MP3 players.
What is needed in the art is a way to enable users to possess a digital music file that is optimized for different hardware platforms on which the music may be played.